1. Field of the Invention
The present invention relates to an apparatus for controlling high speed operation of a motor and a method thereof and, more particularly, to an apparatus for controlling high speed operation of a motor and a method thereof by estimating the position and the speed of the rotor of a synchronous motor without a PI(Proportional plus Integral) regulator to eliminate the users' inconvenience due to gain adjustment of the PI regulator and additionally to secure the reliability of the control of speed and position of a rotor of a synchronous motor.
2. Description of the Conventional Art
In general, the position and the speed of the rotor should be estimated for sensor-less vector control of a permanent magnet synchronous motor (PMSM). The position of the rotor is necessary for reference frame transform, and the speed of the rotor is necessary for speed control.
To estimate the speed and position of the rotor, the position of a rotor and a speed estimator according to a conventional art is composed of a reference frame transformer 110 that converts static coordinate system voltages and currents to synchronous coordinate system voltages and currents; an EEMF (Extended Electromotive Force) estimator 120 that receives inputs from the coordinate-converted voltages and currents and calculates position error; a PI regulator 131 that estimates the speed of the rotor using the position error calculated by the above estimator; and an integrator 132 that estimates the position of the rotor by integrating the estimated speed of the rotor.
In the conventional art, after estimating EEMF that provides error information (êr—error) between the actual position of the rotor (θr) and the estimated position of the rotor ({circumflex over (θ)}r) using static coordinate currents (iαβ) and voltages (vαβ), the position (θr) and speed (ωr) of the rotor that are necessary for vector control are estimated using PLL (Phase Locked Loop), so that the estimated EEMF (Extended Electromotive Force, êq) converges to 0.
FIG. 1 shows an apparatus for controlling high speed operation of a sensor-less PMSM that includes a conventional PI regulator, the PLL is composed a PI regulator and an integrator, and the output of the PI regulator 131 is the estimated speed of the rotor ({circumflex over (ω)}r) and the output of the integrator is the estimated position of the rotor ({circumflex over (θ)}r).
In a conventional art that uses PLL, the estimated performance of the rotor's position and speed depends heavily on the PI regulator's gain since the position and the speed of the rotor are estimated by the PI regulator 131. In other words, if the bandwidth of the PI regulator 131 is too small, in high speed operation the estimated position of the rotor could step out of the actual position.
FIG. 2 is a graph illustrating the magnetic model of PMSM of a conventional art with saliency. If the position and the speed are estimated by the motor parameters of constants in a PMSM with saliency, the occurred motor parameter errors deviate from regular operating points and, finally, the estimation of the position and the speed results in error. To tackle the issue, the magnetic model should be embodied for high accuracy speed control. To implement it according to the conventional art, all the specific points shown in FIG. 2 have to be stored in a memory and the value of the current operating point should be interpolated.
However, the method requires a large amount of data and interpolation calculation, and the implementation thereof is limited by memory and processing power.
Therefore, in the convention art, an additional work to adjust PI gain is necessary, and a difficulty exists because it should be adjusted through many tests.